How to set the color of a selection area on a canvas using FabricJS?

In this article, we are going to learn how to set the color of a selection area on a canvas using FabricJS. We can adjust the color using the selectionColor property.

Syntax

new fabric.Canvas(element: HTMLElement|String, { selectionColor: String }: Object)

Parameters

element − This parameter is the <canvas> element itself which can be derived using document.getElementById() or the id of the <canvas> element itself. The FabricJS canvas will be initialized on this element.
options (optional) − This parameter is an Object which provides additional customizations to our canvas. Using this parameter, properties such as color, cursor, border width and a lot of other properties can be changed related to the canvas, of which selectionColor is a property with which we can indicate the color of the selection. The default value of selectionColor is rgba(100,100,255,0.3).

Example 1

Passing the selectionColor key to the class

The selectionColor property accepts a String which determines the color of the selection. We can use an RGBA value which stands for: red, blue, green and alpha. The alpha parameter specifies the opacity of a color. Let's see a code example of how we can set the color of a selection area in canvas using FabricJS.

<!DOCTYPE html>
<html>
<head>
   <!-- Adding the Fabric JS Library-->
   <script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/510/fabric.min.js"></script>
</head>
<body>
   <h2>Setting the color of a selection area using FabricJs</h2>
   <p>Select an area around the object to see the color of the selection area.</p>
   <canvas id="canvas"></canvas>
   <script>
      // Initiate a canvas instance
      var canvas = new fabric.Canvas("canvas", {
         selectionColor: "rgba(0,0,0,0.4)",
      });
      // Creating an instance of the fabric.Rect class
      var rect = new fabric.Rect({
         left: 170,
         top: 90,
         width: 60,
         height: 80,
         fill: "#006400",
         angle: 90,
      });
      // Adding it to the canvas
      canvas.add(rect);
      canvas.setWidth(document.body.scrollWidth);
      canvas.setHeight(250);
   </script>
</body>
</html>

Example 2

Using a color name instead of an RGBA value

We can also use a specific color instead of using an RGBA value. In this example, the selectionColor property has been set to the color "red".

<!DOCTYPE html>
<html>
<head>
   <!-- Adding the Fabric JS Library-->
   <script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/510/fabric.min.js"></script>
</head>
<body>
   <h2>Setting the color of a selection area using FabricJs</h2>
   <p>Select an area around the object to see the color of the selection area.</p>
   <canvas id="canvas"></canvas>
   <script>
      // Initiate a canvas instance
      var canvas = new fabric.Canvas("canvas", {
         selectionColor: "red",
      });
      // Creating an instance of the fabric.Rect class
      var rect = new fabric.Rect({
         left: 170,
         top: 90,
         width: 60,
         height: 80,
         fill: "#006400",
         angle: 90,
      });
      // Adding it to the canvas
      canvas.add(rect);
      canvas.setWidth(document.body.scrollWidth);
      canvas.setHeight(250);
   </script>
</body>
</html>